Several users on a german hairloss forum claim to have had some initial regrowth success with the antihistamine drug, Cetirizine. It is quite early to tell since they have only been testing it since about 1.5 months, but they all seem very confident that something is happening. Most of them describe some appearance of vellus hair and a strong reduction of scalp itching.
Today one user (Habeeby) posted the following :
Here some news again from me!
My treatment: minox and fin since 4 years. Started Cet a month ago (according to Pilos mixture instructions).
I only take Fin sporadically. Maybe 2-3x per week 1 mg.
I already reported about 2 weeks ago, that small pigmented vellus hairs are appearing
These have now become thicker. The existing hairs look very healthy.
The front is looking very dense again. I now have reached the density that I had 2 years ago.
I am very enthusiastic about Cet. It really is working for me! My scalp is feeling very pleasant. No more itching =)
I want to thank you at this point for your efforts. If I had not stumbled over this forum, I would still have no frontal hairs. And with the shape of my head that looks really weird.
Cetirizin is available as an over the counter drug in Germany/Europe and it is very cheap (roughly 13€/50 tablets).
There are studies which have shown that PGD2 “was clearly reduced by cetirizine treatment”. Also, “the inhibition was most marked during the fifth hour of the reaction when there was a 50% suppression of the PGD2 level by cetirizine”. 
While at the same time another study shows that “Cetirizine (0.1-10 micrograms/ml) enhanced PGE2 release by resting human monocytes”. 
Admittedly, this is all mere humbo jumbo for me since I don’t have the slightest clue what human monocytes are.
I think this stuff might be worth a try (I should be getting my Cet next week) . I am hopeful, yet skeptical because this guy is claiming to have seen increased density/regrowth after just a bit over one month of treatment. I think it really seems too early to be assigning this to Cet. However several others are claiming to be seeing vellus hair as well, so who knows? I hope there’s some truth to it.
If anyone is interested in learning how these guys made a topical from the pills, just let me know and I will translate Pilos instructions.
Pilo seems to be quite knowledgeable and is highly respected on the german hair loss forum for his advice in making topicals.
 Effect of cetirizine on mast cell-mediator release and cellular traffic during the cutaneous late-phase reaction - PubMed
 In vitro effect of cetirizine on ... preview & related info | Mendeley
 Haarausfall - Allgemeines Forum : Sonstige Produkte bei Haarausfall » Cetirizin-Anwender - Teil 1
I would be really glad if we could ignore the trolls on this thread. Iron_Man is already trying to disrupt any non-Gho-related discussion